An ionophore is a compound which is capable of forming a complex with an ion. The organotin compounds used in the present invention are anionic ionophores i.e. they are capable of forming a complex with an anion. The complex may be formed by contacting the anionic ionophore with a solution containing one or more anions. The formation of such complexes finds use in a wide variety of applications. For example, the complex forming reaction may be utilised in a method for determining ion concentration.
There are many situations in which the ability to determine the activities of ions in fluids would be beneficial. One method of ion measurement involves the use of ion sensitive electrode potentiometry. The use of ion selective electrodes and related sensors depends on the measurement of membrane potentials which arise as a result of the partition of ions between an ion selective membrane and aqueous phases. These potentials cannot be measured independently, but can be deduced from the voltage generated by a complete electrochemical cell comprising an ion selective electrode and a reference electrode.
Tri-n-alkyl tin halides and related compounds have been described as anion carriers in U. Wuthier et al, Anal. Chem., 1984, 56, 535 and U. Wuthier et al, Helv. Chim. Acta., 1985, 68, 1822. These papers describe the incorporation of the compounds in solvent polymeric membranes of anion selective electrodes. A disadvantage of these compounds is that they are hydrolytically unstable and readily decompose under basic conditions.